Computer scientist Fabrice Bellard says he's calculated pi to a whopping 2.7 trillion digits - a Herculean task which took a humble desktop PC 131 days.
According to the BBC, the previous record of 2.6 trillion digits was held by Daisuke Takahashi of Japan's University of Tsukuba. That number-crunching exercise took just 29 …

I disagree

A number that requires over a Terabyte just to store is completely useless, I mean what would you use it for ? How much paper would be required to print it out ? Can kids use it in their homework? assuming the national curriculum has room for something esoteric like geometry, now that we spend so much time testing and indoctrinating....

How can we check he got it right ? I mean right to the last digit, He might have just done the first few thousand and then stuck any old random stuff on the end ....

Of course the numbers ar ecorrect

>How can we check he got it right ? I mean right to the last digit, He might have just done the first few thousand and then stuck any old random stuff on the end ....

Simply by checking the code he's going to release, and by analysing it and seeing it is indeed equivalent to one of the many ways of computing Pi mathematically.

And of course, you can also match it against the 2.7 trillions decimals of the previous record-holder, and since the record will always be pushed further, it would be simply stupid to lie, since then your reputation would be destroyed once the next record comes in and the discrepancies force a check to see who was wrong, the previous or the new record holder.

So, to sum it up, no, he CAN'T make up the decimals without being spotted as a fool and cheater by scientists very quickly.

re Of course the numbers ar ecorrect

Wow...

Oh well that'll come in handy

I don't understand why people do stuff like this.

It's not interesting or useful at all. Who the frig is going to use that number for _anything_ in reality? Seriously if anyone can explain that then tell me, because I'd be really interested in understanding the mentality of people like this.

Normal proof?

No chance. 2.7x10^12 is nowhere near enough to even being to prove pi isn't normal, let alone get closer to proving it is. Suppose pi (in decimal) starts recursing 4242424242 from, oh, a googleplex onwards? There's not enough storage anywhere to hold pi to that many digits and even if there was supposing the recursion stops at a googleplexplex and then continues being random after that: those "few" digits would just be a little curiosity.

Infinity is a big number.

And to all those other peope, pi comes up in so many more places than circles you wouldn't believe it.

Of course there is a purpose...

Testing

"if your computer isn't operating flawlessly some of those digits will be wrong"

So after 181 days you will be told either there is something wrong or there is nothing wrong. I'm sure we can devise better tests than that. Actually it would probably take less than 181 days to write the tests.

Talking of testing.

If a use of a very precise pi is to validate that your humungous number-cruncher and it's algorithms are working correctly and nobody's calculated pi to that precision before, it does beg the question:

How the fuck did he check the answer he got?

There can't be much point using his 1.7 trillion digit pi to validate your shiny supercomputer cluster against if it's not been validated now, is there?

Safety in numbers

Useful? Yes, actually...

The impressive thing isn't that he has calculated such a massive number, just that he has written an algorithm that can do it on a high end desktop rather than a supercomputer, which is nothing to be sneezed at.

Commen-tarding on the article though, it contains less info than the beeb article and not even a cursory examination of what kind of algorithm expertise it would need - I expected better from El Reg.

I bet

@Supertim - Humble Desktop?

An i7 with 6gb of RAM and a few extra disks thrown in is *not* something special, or top flight - it's a standard build with some extra disk. It is a humble desktop. It's barely any more sophisticated than my £500 Q6600/8gb/HD4850 build, just with a bit more performance and more disk.

You can buy the components for an i7 machine of this ilk for £500 if you look around - give it a power supply, cheap GPU and case and you'll be looking at £600-650, then add your hard drives.

So it's a humble desktop in my book. It's not like he used a dual socket mobo and fibre-channel for the storage!

Cool!

Never thought about that before, but yeah, this PI generation as computer test is a great idea! Level 5 diagnostic Mr. Spock: have the CPU cores calculate out to like 100 places. Level 1 diagnostic Mr. Spock: have the CPU cores calculate out to like a trillion places. After all, even in the future a proper in-depth diagnostic should retard and shut down the systems to make the ship more vulnerable to attack--after all, what is life, and plot, without risk.

That's nothing

How to calculate pi?

So I take it that the last 100 billion digits that broke the record are a result of actually recording the output rather than doing extra calculations? Does it take twice as long to 'calculate' 2 trillion places compared to 1 trillion places?

Anyway when will they release it, I want to find my phone number since it's not available within the first 200 million places! :(

I bet Archamedes never thought of that.

Bignums or ReallyBigNums

The article says that bignum systems are "... limited only by the computer system's available memory". Assuming that means virtual memory, that's true of most bignum systems. This guy went beyond that - it would take roughly 1TB of memory to hold the resulting number, and he had "only" 6GB. (And that's without taking into account that calculations at this precision require more than one number of this size.)

Don't tell me he had all that hard disk space as virtual memory, because I will find it hard to believe. To get that sort of performance, he'd almost _have_ to do it himself, rather than relying on the OS to page out the right parts of the number.

Impressive feat. Now let's see it put to some other use, because I'm sure he had one in mind before he started!